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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4><a name = "tag_000_007_439">&nbsp;</a>NAME</h4><blockquote>
logb - radix-independent exponent
</blockquote><h4><a name = "tag_000_007_440">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="math.h.html">math.h</a>&gt;

double logb(double <i>x</i>);
</code>
</pre>
</blockquote><h4><a name = "tag_000_007_441">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>logb()</i>
function computes the exponent of <i>x</i>, which is the integral part of
log<i><sub>r</sub></i>&nbsp; |&nbsp;<i>x</i>&nbsp;|&nbsp;,
as a signed floating point value, for non-zero <i>x</i>,
where <i>r</i> is the radix of the machine's floating-point arithmetic.
</blockquote><h4><a name = "tag_000_007_442">&nbsp;</a>RETURN VALUE</h4><blockquote>
Upon successful completion,
<i>logb()</i>
returns the exponent of <i>x</i>.
<p>
If <i>x</i> is 0.0,
<i>logb()</i>
returns -HUGE_VAL and sets <i>errno</i> to [EDOM].
<p>
If <i>x</i> is &plusmn;Inf,
<i>logb()</i>
returns +Inf.
<p>
If <i>x</i> is NaN,
<i>logb()</i>
returns NaN and may set <i>errno</i> to [EDOM].
</blockquote><h4><a name = "tag_000_007_443">&nbsp;</a>ERRORS</h4><blockquote>
The
<i>logb()</i>
function will fail if:
<dl compact>

<dt>[EDOM]<dd>
The <i>x</i> argument is 0.0.

</dl>
<p>
The
<i>logb()</i>
function may fail if:
<dl compact>

<dt>[EDOM]<dd>
The <i>x</i> argument is NaN.

</dl>
</blockquote><h4><a name = "tag_000_007_444">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_445">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_446">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_447">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="ilogb.html">ilogb()</a></i>,
<i><a href="math.h.html">&lt;math.h&gt;</a></i>.
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UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]

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